In the Malvern district it is a mass of finely Levigated argillaceous matter, attaining, according to Professor Phillips, a thickness of 640 feet, but it is sometimes more than 1000 feet thick in Wales, and is worked for flag-stones and slates.
"The Student's Elements of Geology"
Sir Charles Lyell
It is usually Levigated with slab and roller, and made into sour cakes.
"First Footsteps in East Africa or, an Exploration of Harar"
Richard F. Burton
When the design is visible, well defined and brownish, the proof, being removed from the printing frame, is rubbed with very finely powdered, or, better, Levigated graphite, and, this done, immersed in cold water for from fifteen to twenty minutes, when by gently rubbing it under a jet of water with a soft rag, or with a sponge imbued with water, the albumen is washed off from the parts not acted on, leaving the design on a perfectly white ground.
"Photographic Reproduction Processes"
P.C. Duchochois